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Forensic EngineeringVolume 170 Issue FE4

Grounds for concern: geotechnical issuesfrom some recent construction casesTonks, Gallagher and Nettleton

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Proceedings of the Institution of Civil EngineersForensic Engineering 170 November 2017 Issue FE4Pages 157–164 http://dx.doi.org/10.1680/jfoen.17.00008Paper 1700008Received 07/03/2017 Accepted 09/10/2017Published online 14/11/2017Keywords: failure/geotechnical engineering/slopes – stabilisation

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Grounds for concern: geotechnical issues fromsome recent construction cases
1 David Tonks PhD, CEng, CGeol, FICE, MAE
[ Da

Technical Director, Coffey Geotechnics, Manchester, UK(corresponding author: [email protected])

vid Michael Tonks] on [08/12/17]. Copyright © ICE Publishing, all rights r

2 Eugene Gallagher CEng, FICE

eserv

Technical Director, Coffey Geotechnics, Manchester, UK
3 Ian Nettleton Eur Geol, CEng, MIMM, CGeol, FGS
Technical Director, Coffey Geotechnics, Manchester, UK

1 2 3

There continue to be many substantial cases of engineering failures associated with the ground, some veryproblematic and expensive. This is despite most of the technical issues being well known and the subject of muchstudy and comment. Too often for non-specialists, the lessons continue to be learnt only by bitter experience. Thispaper reviews various issues and risks from the perspective of the authors’ practical experiences, mostly acting inexpert roles investigating and advising on numerous geotechnical cases related to construction. These involve awide variety of types of failures and circumstances. They include foundations, shallow and deep; slopes andinfrastructure for road, rail and utilities; and mining and waste industries. The examples select some of the moresubstantial cases, with costs frequently of many millions of pounds. None here involved loss of life, but in severalcases, this was fortuitous. Some significant implications and learning points are discussed.

1. IntroductionThis paper reviews findings from more than 100 geotechnicalconstruction-related cases with which the authors have beendirectly involved, mostly in an expert capacity in investigationand dispute resolution. Most have involved legal representatives,insurers, clients and asset owners, consultants, contractors andspecialist suppliers. Most are in the UK, but a few areinternational cases. They cover most areas of civil engineeringand most types of contractual arrangements. The authors alsodraw on many other reported cases that they have had reason tostudy. This paper excludes non-construction cases – for example,natural geohazards – for another paper, but many similar issuesand comments arise.

Specific details have been kept appropriately limited andconfidential, noting that the roles of parties are often complex andat issue. Aspects are often known only partially to different parties.Opinions are necessarily subjective; the authors would be glad toset the record straight where they might have seen only a part ofthe picture. They act primarily as consultants and designers in therelevant fields. Their roles in cases described here have been aboutequally for claimants and defendants and occasionally as singlejoint experts or other independent roles. Some common themes arediscussed, notably failures to interpret the ground adequately. Mostof the problems were reasonably avoidable had appropriate existingknowledge been brought to bear at a suitable time. Somerecommendations are given for improved identification, reduction,management and communication of risks in the ground.

About half of the cases are categorised as substantial, typicallyinvolving claims in excess of £1 million and sizable damage anddelay. About 20% are termed major, broadly involving costsexceeding £10 million, in some cases over £100 million, and majorconsequences. Related issues are identified as having proportionateconsequences, to enable some broad conclusions to be drawn. It isworth adding that some of the smaller cases have been among themost technically interesting and challenging. It is also important toacknowledge the personal aspects where lives may be greatlyaffected. This ranges from traumatic incidents and events moving athigh speed, through managing consequences and finding the ‘bestway out’, to the relentless grind of legal or other resolution processes.

More than 80% of the cases involved claims against thedesigners, and over 50% involved the main contractor. Around35% involved both, often with substantial issues between designand construction, sometimes quite complex and subtle. Someinvolved several designers or specialists – for example, a leadcivil/structural designer, with a geotechnical specialist or supplier.When things go wrong in the ground, a client may not know keyfacts and may be left to pursue several parties who may contestmatters long and hard. He/she often finds himself/herself carryingvery substantial risks and disturbance to his/her operations orplans, together with the worries and responsibilities of finding asatisfactory way forward.

In most cases, it was evident that there had been a substantial lossand the issues were essentially who, if anyone, may be liable.

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Most were failures, rather than contractual claims, which tend tobe more quantum based, but sometimes involve substantialliability or geotechnical issues. A recent example involved severalgeotechnical experts arguing the merits of an onerous fillspecification, zealously interpreted, expensively and wrongly inthe contractor’s view. Nothing failed, nor was likely to, but thecosts ran into millions of pounds and someone had to pay!

Most of the cases were settled by some form of alternative disputeresolution, with only about 20% getting to court or other ‘forum’

with a clear finding of liability. Around 20% were essentiallyunsuccessful, including some not pursued for various reasons. It issometimes an expert’s role to advise that a claim is not substantiatedor, conversely, that an issue may be technically indefensible. Themajority of claimants had a measure of success, but few goteverything they asked for. Many cases also incurred substantialcosts. Although rarely very transparent, the true costs in time ofdisruption and disturbance to the parties are often high, sometimesoutweighing the sums claimed and making settlement difficult, ascases proceed and costs grow. While project owners naturally wantto pass the risks in the ground to others, it is evident that these often‘come back to bite’. Perhaps the most telling issue is reluctance tospend money ‘up front’ on ground investigations and particularly oninterpretation. This appears to have increased in recent years,perhaps particularly where organisations have limited in-houseengineering expertise or are not inclined to listen to engineeringadvisers. This is sometimes said to be ‘commercial’ or ‘cost driven’,perhaps ironically where large sums have hung on the absence orshortcomings in investigation or interpretation costing a fewthousand pounds. Where a construction contract is let without anadequate site investigation, the client team owns a very substantialrisk, which is unlikely to be mitigated fully by any amount of legalmanoeuvring, insurance, project management or whatever devices.

2. Geotechnical hazards and riskmanagement

Much has been written on geohazards, geotechnical and geologicalrisk management (GeoRM). The interested reader is referred to vanStaveren (2006), SISG (2013) and ISSMGE TC304 (2013), whichlead to numerous links. The key points here are the following.

■ Geotechnical risk should be ‘owned’ by professionals withappropriate expertise (as should each type of risk identified).

■ GeoRM needs to be suitably integrated within project riskmanagement. In practice, this means better integration andincorporation of experienced geotechnical professionals withinthe project core team.

An example is a major failure a few years ago where a project riskregister listed insurance as the relevant mitigation measure againsttunnel collapse, but omitted appropriate site observation andmonitoring. This should have identified construction proceduresthat differed significantly from the design approach and thendeveloping movements of the tunnel crown greatly exceeding thedesign predictions. Appropriate interpretation should have averted

158ed by [ David Michael Tonks] on [08/12/17]. Copyright © ICE Publishing, all ri

the ensuing collapse, which proved enormously costly and, but forfortune, could well have led to major loss of life. There have beenother comparable cases that were not so fortunate, avoidable bymonitoring and geotechnical expertise on site.

Ground is naturally variable and uncertain, fundamentallydifferent from most other engineering materials and systems, forwhich quality and behaviours can be defined with great precisionand confidence. Variable stresses, histories, groundwater, drainageand environmental conditions can have significant influence.Engineering standards tend to be codified for defined productsand do not address these issues particularly well; more risk-basedapproaches would assist. The Institution of Civil Engineers’ (ICE)recent Manual of Geotechnical Engineering (Burland et al., 2012)discusses some code shortcomings in relation to this and collatesa vast amount of authoritative information.

Case histories have always been crucial to safe and effectiveground engineering (see e.g. Charles, 2008) and go hand in handwith sound theory and calculations. A designer should have athorough command of comparable experiences and case histories,of both successes and failures. An observational approach is alwaysappropriate in the ground. This requires experienced personnel inclose contact with the works, empowered to exercise soundengineering judgements as works proceed. This has been theessence of professional civil engineering from early history,enshrined in developed and ‘well-winnowed’ experience. Asprocedures have become increasingly commoditised and automated,there has been a tendency to subjugate this and reduce or dispensewith technical site expertise, with some serious consequences.

A subset of the observational approach is the observationalmethod (OM) (Ciria, 1999; Peck, 1969). This prescribes decision-making and response procedures based on monitoring, whichpermit economic, sometimes quite bold, construction methods,with potentially large savings in cost and time. Such should beonly in the hands of experienced professionals, who can fullyunderstand the risks and adjust to the feedback in good time.There must always be safe and practical fallback options. Thesuccess of the method is consistent with the fact that none of thecases here relate to truly OM projects.

2.1 Soft and marginal soils including fillsA large proportion of ground-related problems arise fromconstruction on soft ground, including many types of madeground or fill. Such soils are prone to settlements, which canoccur rapidly on granular soils but can continue for many years inclays, peats and some made ground. A distinction must be madewith engineered fills, which are closely specified, suitablyselected, placed and compacted to a specification – in effectquality assured – and for which records should be available,increasingly so nowadays. Some loose soils are prone toliquefaction or flow slides. Most historical cases in the UK havelong since been identified and addressed. However, and despite allthe warnings of history, there continue to be serious incidents.

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In recent years, the authors have addressed several such failuresand there have been a number of major incidents worldwide.

Table 1 summarises the authors’ experience of over 100 substantialsoft-ground projects. Most were relatively successful but about 40%encountered significant problems. Most of these cases involvedseveral issues as indicated. ‘Major’ problems include very lengthydelays, highly disproportionate costs and major litigations.

An extreme case involved very large settlements on a housingdevelopment built over a bog, with some 7 m of peat and verysoft alluvium below. The houses were satisfactorily piled, but theinfrastructure was constructed as a shallow stone platform ongeogrid, with no special measures to address the verycompressible ground below. As this settled, ground levels weremade up, greatly increasing the loading and exacerbating theproblems, particularly with the drainage. The worst settlementswere approaching 3 m and still continuing at over 100 mm/year inplaces after about 10 years. The consolidation and particularlycreep-type settlements of the peat had been grosslyunderestimated. Despite valiant works by the developer, the roads,services and plot surrounds became unmanageable. Figure 1shows an example of a driveway, originally flat, but eventually

[ David Michael Tonks] on [08/12/17]. Copyright © ICE Publishing, all rights r

sloping at a steep angle and falling away such that the garagecould not be accessed and a step formed.

The 4-month court case included a claim of failure to employsuitable geotechnical expertise. Eventually some 40 houses weredemolished and the remainder of the estate required an expensivepiled road to maintain access. The authors have advised on manysimilar but less dramatic cases involving long-term ongoingsettlements on peat and other marginal soils. Some furtherexamples of soft-ground cases are discussed by Tonks andAntonopoulos (2015).

The lessons to be learnt are mainly the importance of involving ahigh level of geotechnical expertise from the outset and as worksprogress. Amounts and particularly rates of consolidationsettlements are notoriously difficult to predict and can be veryvariable with varying conditions. However, many quite oneroussites have been economically developed using suitable groundimprovement technologies. Predictions can be greatly improvedby monitoring as work proceeds, particularly where suchdevelopments proceed over several years. Risks and uncertaintiescan be reduced (but not eliminated) by high-quality investigationsand testing, including field trials (Tonks and Ameratunga, 2012).

2.2 Shallow foundations and ground-bearing slabsShallow foundations are normally designed to have high factors ofsafety against bearing capacity failure (collapse/ultimate limit state).Problems mostly relate to excessive movements and associateddamage. Long experience has shown that keeping applied stressesto less than a third of codified or calculated ultimate capacity keepssettlements acceptable for routine shallow foundations to preventcracking or distress. There are methods for more sophisticatedanalyses for the extensive range of foundation and groundconditions. However, there continue to be failures, attributablelargely to lack of investigation, interpretation or awareness.

Figure 2 shows the wall of an old mill that collapsed when theadjacent ground was excavated without due investigation orconsideration. The foundation was very shallow and varied inlevel. The coloured balls visible on the ground are from a nurseryin the building! Staff saw cracks appearing and evacuated thechildren only minutes before the collapse. There was no properinvolvement of geotechnical expertise in design or constructionand no desk study or due investigation, which could readily haveidentified and prevented the serious problems here.

The authors have encountered many other cases of collapses orunacceptable movements of foundations, due to, among otherthings, lack of allowance for adjacent slopes or groundwater orfailure to identify ground conditions correctly. Many old footingsand other works were built very economically, not enjoyingmodern factors of safety. Some are ‘on a knife edge’.

Ground-bearing floor slabs continue to give a substantial numberof problem cases. Slab movements and damage can often be quite

Table 1. Cases showing construction problems on softground – overview

Topic
Total cases Problems
%
Significant Major
Soft-ground cases
130 37 40 8 Settlement 74 41 25 5 Stability 34 68 20 3 Ground improvement 32 44 11 3 Piling 20 40 6 2 Shallow foundations 54 28 13 2 Construction 75 13 8 2 Programme/delays 75 35 20 6
Figure 1. Housing with oversteep drive – after nearly 3 msettlement on peat

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readily remedied by injection grouting methods, relevelling totolerances of within a few millimetres. In several cases, this wasnot done for a long time, leading to disproportionate concerns andhigh costs for the affected parties. When disputes arise, there isunderstandable pressure for a full and final solution. However,such cases can sometimes be proactively managed for modestcost. This can also greatly mitigate problems for the time beingwhile matters are being resolved.

There have been several recent cases of significant settlementsdisrupting operations in warehouses on various type of slabs,some ground-bearing and some on piles or ground improvements.A key issue can be lack of experienced site supervisory personnelvalidating records or identifying and investigating possibleanomalous behaviour. Some pile types allow real-time ‘feedback’to validate that suitable depths and capacities have been reached.There have always been occasional problems, but most are wellknown to piling and geotechnical specialists. A review of theauthors’ cases suggests that all were avoidable had availableknowledge and good practice been followed.

2.3 Landslides, slopes and stabilisation worksThe authors have long been involved in a very wide range ofslope projects for road, rail and various public or privatedevelopments. The vast majority on their files have either beennew works designed and constructed satisfactorily or existing,often quite old ‘assets’, identified as at risk by standard inspectionprocedures and suitably managed or remediated. However, eachyear, the authors encounter a number of failures, mostly requiringemergency works and some of which involve substantialinquiries, forensic investigations or legal cases.

Nettleton et al. (2010) discuss a number of examples. Spaceprecludes detail here, but the following summarises some keypoints and common features.


■ The engineering geology is crucial. Most soil and rock types(at least in the UK) have been studied, many in much detail,and there are numerous case studies, which should beidentified in desk studies (but all too frequently are not).

■ High-quality fieldwork and attention to detail are veryimportant. Techniques such as digital terrain models haveadvanced greatly in recent years and allow far more attentionto the three-dimensional (3D) geometry and geology.

■ There continue to be many incidents due to natural or climaticconditions, notably high antecedent rainfall, where surfaceand groundwater drainage needed to be understood andmanaged better during construction.

■ Slopes in clay soils and rocks, including mudrocks, can stand atsteep angles in the short term but fail, sometimes dramatically,with time due to changes in pore-water pressure. This followswell-understood geotechnical principles (effective stress) butremains a mystery to most non-specialists.

■ There are various other forms of soil and slope deterioration,including weathering, again increasingly being understoodfrom careful studies, including forensic investigations.

Major generic slope failure types include Hong Kong landslides,subject to intensive studies and works since several eventscausing collapse of buildings and fatalities in the 1970s, andScottish debris flows, subject to much study after several seriousincidents following heavy rainfalls in 2004, notably closing theA85 Road in Glen Ogle (Winter et al., 2005). Perhaps the mostchallenging constructed rock slopes on the UK transport networkare at Stromeferry. About 6 km of major rock slopes wereoriginally blasted at steep angles for construction of the rail lineto Kyle of Lochalsh along the edge of Loch Carron. They werethen blasted back further in the 1950s to construct a single-trackroad on the landward side. This resulted in several rock slides anda major legal case against the designers, with fears of substantialfurther mass movements. Figure 3 shows one of the affectedareas, where an avalanche shelter was constructed to protect theroad and rail. Many of the rock faces exceed 30 m direct height,with substantial natural slopes above and ongoing debris flows aswell as rock falls. The slopes have been subject to extensivestudies and progressively stabilised by netting, bolts, anchors andother details over many years (Nettleton et al., 2010).

Similar issues have arisen extensively elsewhere in Scotland andother mountainous areas of the UK and have led to substantialresearch and development. The risks are now well known to themajor stakeholders and are managed accordingly but remainproblematic. Potentially expensive works have to be prioritisedand balanced with other needs on a risk basis. Incidents still canand do occur and the resolution processes can be difficult. Someparties have developed extensive procedures to manage slopesand other geohazards. However, there are many other owners withlesser resources and expertise, faced with managing a limitednumber of slopes. Difficult cases still arise for both natural andman-made hazards, not least concerning failures of slopes withseveral owners and ‘outside parties’.

Figure 2. Collapse of wall on shallow footing

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The general lesson to be learnt is the importance of a reasonablyproactive approach to slope management. The authors continue toencounter too many cases where a geotechnical inspection wouldhave alerted the parties and should have led to suitable actions.Tonks et al. (2008) discuss this further in terms of a proportionateapproach to hazard assessment. A positive example is a localauthority on the UK coast with extensive roads, housing and otherassets above and below cliffs. After some years of considerableongoing problems, a proactive slope management strategy has beendeveloped to allow timely interventions on a prioritised basis.

2.4 Waste including geocontainment and barrier systemsWaste and landfill cases frequently include significant geotechnicalissues. Some recent cases involve substantial slope stability andsettlement issues, in some instances exacerbated by the phasing ofdevelopments over many years. Landfill cells are typicallyconstructed at intervals during the lengthy life of a large facility.However, the groundwater or ground conditions may change withtime, and investigations are commonly not repeated for later phases.

At a site in a former opencast coal mine, artesian groundwaterconditions developed for one of the later cells, leading to upliftpressures on the liner. Figure 4 shows the side-slope and theresultant failure after the geomembrane had been removed for


forensic investigations. This cell had to be redesigned to includesubstantial underdrainage and required a complete rebuild.Remedial costs substantially exceeded the original constructioncosts and delay to operations totalled about a year.

Knowledge of geosynthetic (plastic) materials has developedrapidly since the 1980s and is now a mature technologydiscipline, sometimes termed ‘geocontainment’. Numerousproblem cases in the early, ‘innovative’ stages of development ledto extensive specifications and procedures for a high level ofconstruction quality assurance (CQA). These are nowcommonplace in landfill sites, but problem cases still arise for lesshighly engineered and regulated facilities.

Investigations into a 1980–1990s landfill cap at a major facility innorth-west England (Gallagher et al., 2016) recently revealedpreviously unsuspected issues. The geomembrane itself hadperformed well, with little evidence of degradation overapproaching 30 years. However, extensive tear-type damage wasuncovered, notwithstanding reported CQA of the liner welding atthe time. The damage is attributed to the original constructionpractice, with the plant getting bogged on unduly soft cover soilsand damaging the as-placed geomembrane. Figure 5 shows onelocation of damage exposed when cover soils were removed. Thehorizontal pipe is a land drain. The adjacent vertical pipe is a gasvent, with a boot detail that was found satisfactory.

3. Some general findings and key issuesFigure 6 gives an overview of some of the main causes ofground-related failures, expressed as percentages of the authors’cases in which the issues featured significantly. Most casesinvolved the interaction of several key geotechnical issues, withother issues frequently having some influence.

3.1 Geotechnical expertiseA large proportion of the cases involve allegations of inadequategeotechnical design and/or interpretation, albeit not allsubstantiated. Some 70% of the cases examined lacked the

Figure 3. Steep slopes above road and rail at Stromeferry

Figure 4. Failure of a landfill liner

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expertise that geotechnical professionals would normallyrecommend for a project of comparable nature. In a few cases,experienced personnel arguably did not have the role to addressthe relevant issues. A few cases involved mistakes or errors ofjudgement that could have been eradicated by independentchecking or better risk management.

Few of the causation issues might be considered genuinelyunforeseeable. So-called unforeseen ground conditions have alwaysbeen a significant feature of construction works. However,nowadays, most cases relate to inadequate geotechnical interpretation


and advice, almost always failure to procure or apply such. Most ofthe problems identified would be known to experienced geotechnicalpractitioners and are therefore ‘foreseeable’. The Register of GroundEngineering Professionals has been established by the ICE,Geological Society and Institute of Materials, Minerals and Miningto address this concern (ICE et al., 2013). This sets minimumstandards of training and expertise commensurable with thegeotechnical risks, now advocated in UK practice. The key issueremains whether clients will insist on using this available expertise;some of the more sophisticated organisations, particularly in thegovernment and public sector, are requiring such for projects wheregeotechnical issues may be significant.

Inadequate investigation is frequently cited as a significant causeof geotechnical failures. The authors have sought to distinguishthe factual investigation per se from the interpretation; their datasuggest the latter is by far the greater issue. The authors wereinterested to note that ground investigation specialist contractorsfeatured in less than 10% of the cases in their records. In severalcases where they did, the issues were primarily matters ofinterpretation. That said, in many of the cases, the groundinvestigation was less than desirable; this simply did not featureas a main cause. There is a widespread perception amonggeotechnical specialists that an insufficient amount is spent oninvestigations, and the authors would not dispute that. Forinstance, piling and foundation specialists commonly complain ofinadequacies in the amount and quality of information (exceptingperhaps the more geotechnically advanced schemes). It appearsthat many projects ‘manage’ this risk by taking a precautionaryapproach. In essence, this means more conservative design and

Figure 5. Damage to landfill liner associated with construction

Unforeseeable

Services

Miscellaneous

Groundwater

Slabs and shallow foundations

Ground improvement

Piling and sheet piling

Slopes and retaining structures

Soft/marginal ground

Construction

Design

Geotechnical interpretation

Inadaquate investigation

0 10 20 30 40 50 60 70Percentage

Figure 6. Main geotechnical issues (percentage identified in 110 cases)

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construction. Money spent on appropriate investigations is neverwasted. The costs rarely reach 1% of project costs and are insome cases negligible. In contrast, the costs of ground-relatedissues commonly exceed 10%, and occasionally 50%, of projectcosts. ‘Savings’ are illusory, leading at best to wasted money orovercautious designs (not for this paper) but in many cases tomuch direct cost and delay.

3.2 Construction issuesAbout 50% of the cases include significant workmanship or othersite-related issues. Many involve inadequate records or siteinspections. The authors are well aware of cases where thepresence of experienced site personnel would most probably haveidentified that the construction or ground revealed differed fromexpectations and significant failures could have been averted. Theperceived reductions in experienced geotechnical (and indeedother civil engineering) professionals on site over recent years, atleast in some places, appear of concern and a significant factor inongoing ground-related failures.

3.3 Existing assets, maintenance and sustainabilityAn important and growing risk can be identified concerningexisting assets in the ground. It is fortunate and timely thatBuilding Information Modelling (BIM) and modern computer-based systems greatly enhance the keeping of records and theability to use these. However, there remain extensive problems withthe lack of old records. There are numerous instances of damageand delay from works encountering unexpected utilities, normallybest handled by a good co-operative working with the asset owners,but occasionally warranting expert or forensic advice. AlthoughBIM is a relatively recent development, geotechnical professionalshave faced the challenges of managing large data sets of 3Dtopographical and subsurface data for several decades, and it isroutine to develop complex ground models that evolve withprojects. A significant difference between geotechnics and otherengineering fields is the importance of knowledgeable interpretationof field data to develop ground models and engineering parametersthat are representative and robust, notwithstanding the intrinsicvariabilities and uncertainties in the ground.

3.4 Consequential and contractual aspectsMany cases involved major knock-on problems, particularly asgeotechnical issues tend to arise at an early stage in projects. Therisks can be highly disproportionate to the direct costs of thegeotechnical works. The authors have encountered some majorfailures on turnkey and engineer–procure–construct projectswhere the geotechnical issues simply did not feature adequately inthe overall project risk profile, at least until far too late. A goodexample is a major rail project that foundered on continuingsettlements on soft ground, eventually being determined and re-letwith major delay. Costs in dispute were several hundred millionpounds. Various solutions could have been implemented for amodest cost had they been identified by appropriate investigationand expertise at an early stage. By the time that the importance ofthe geotechnical issues was identified, it was far too late for the


scheme to be completed at anywhere near the contract period orprice. The importance of adequately identifying geotechnical risksat the earliest appropriate time cannot be overstated. This hasbeen highlighted on many occasions over the years; see, forexample, Thompson (1998). Unless or until this has been done,considerable grounds for concern remain.

4. Concluding remarksThis paper has drawn attention to the substantial risks involvedwith construction in the ground, with many examples of failuresand lessons to be drawn from these. Such cases continue withundue regularity. Although little in the ground is now trulyunforeseeable, at least in the UK and for many developedcountries, much continues to be unforeseen for a variety ofreasons. This paper points to the very extensive knowledge thathas been hard-won over time and the importance of obtainingtimely and proportionate advice which is available.

There is a well-known aphorism that ‘you pay for a groundinvestigation whether you have one or not’. This paper focuses onthe importance of experienced interpretation thereof throughoutthe course of a project in the ground. The lack of such still toofrequently poses exceptional risks that continue to affectconstruction unduly. The industry has a variable recordconcerning risks, from very sophisticated at the high end topatchy in places elsewhere. Many experienced client bodies havedeep understandings of ground-related risks, but others do not,and too many projects continue to be seriously affected. It ishoped that this paper makes some contribution to improvedunderstanding and practice, in a form accessible to the wide rangeof key professionals and decision makers.

It seems appropriate to venture some comment on the seeminglyincreasing number of construction failures related to the ground,contrasted with the vast increases in knowledge, such that theunderlying science and expertise may be considered quite mature.Some projects have become far more complex; many of the casescited involve complicated interactions, rather than a singleoverriding cause, making due resolution particularly difficult, notleast for clients and advisers dragged into seemingly interminabletechnical detail. Few of the cases are centred on true innovation orthe bolder high-level schemes, which attract commensurate levelsof risk management. Most cases involve fairly routine projects,but where the complexities of the ground engineering behaviourhave not been duly recognised. The authors are led to theconclusion that the overwhelming majority of issues arise fromhuman factors rather than the ground itself. It remains disturbingto encounter cases where those working ‘at the coalface’ are notprovided with the technical support needed.

Finally, it is of course important to maintain due proportion. Themany cases cited relate to the authors’ practice areas on such butremain a small sample compared to the vast number of works thataddress the risks in the ground with ever-increasing success ineconomy and safety.

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AcknowledgementsThe authors gratefully acknowledge the many parties that they havebeen privileged to work with on the cases drawn on herein.Circumstances surrounding failures and forensic cases are oftenunavoidably intense and stressful. Almost invariably, those involvedhave been courteous and professional in seeking to resolve mattersand move forward in positive ways. This has often been fundamentalto mitigating loss and together engineering the best way out.

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Gallagher EM, Tonks DM, Shevelan J, Belton AR and Blackmore RE (2016)Investigations of geomembrane integrity within a 25-year old landfillcapping. Geotextiles and Geomembranes 44: 770–780.

ICE (Institution of Civil Engineers), Geological Society and Institute ofMaterials, Minerals and Mining (IMMM) (2013) UK Register ofGround Engineering Professional. ICE, London, UK, ICE3009(4)a.

ISSMGE (International Society for Soil Mechanics and GeotechnicalEngineering) TC304 (2013) Task Force 3 International State ofthe Art Report on Integrating Geotechnical Risk Management in


Project Risk Management: Main and Country Reports. ISSMGE,London, UK.

Nettleton IM, Tonks DM, Denney RM and Hurworth G (2010) Recent UKexperiences in investigation, design and assessment and managementof hard rock slopes. Proceedings of Geo2010, Calgary, AB, Canada,pp. 939–946.

Peck RB (1969) Advantages and limitations of the observational methodin applied soil mechanics. Géotechnique 19(2): 171–187, https://doi.org/10.1680/geot.1969.19.2.171.

SISG (Site Investigation Steering Group) (2013) Effective SiteInvestigation. Thomas Telford, London, UK.

Thompson RP (1998) The value of timely hazard identification.In The Value of Geotechnics in Construction. CRC, London, UK,pp. 3–11.

Tonks DM and Ameratunga J (2012) Trial embankments to reducegeotechnical risks on poor ground. Proceedings of the 11thANZ Conference on Geomechanics, Melbourne, Australia,pp. 1473–1478.

Tonks DM and Antonopoulos I (2015) Construction risks on soft ground.Proceedings of the 12th ANZ Conference on Geomechanics,Wellington, New Zealand.

Tonks DM, Nettleton IM and Denney R (2008) Some developments in rockslope hazard assessments for road and rail. Proceedings of the 1stInternational Conference on Transportation Geotechnics,Nottingham, UK, pp. 343–348.

van Staveren M (2006) Uncertainty and Ground Conditions: a RiskManagement Approach. Butterworth-Heinemann/Elsevier, Oxford, UK.

Winter MG, Macgregor F and Shackman L (2005) Scottish Road NetworkLandslides Study. The Scottish Executive, Edinburgh, UK.

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